Simple fiber optic seismometer for harsh environments

Abstract

Disclosed is a sensor capable of measuring motion in a harsh environment. The sensor uses a fiber optic sensor element formed within a core of an optical fiber that is disposed within an enclosure made of a high strength, corrosion-resistant material. The optical fiber is attached to a supporting fixture in a cantilever fashion so that the intrinsic internal mass of the optical fiber has the freedom to be affected by gravity so that an environmental disturbance acting on the sensor results in a bending strain being applied to the optical fiber. A Bragg grating is located at the bending portion of the optical fiber. The modulation of an optical signal promulgating through the optical fiber is sensed using conventional means and used to measure the magnitude of the environmental disturbance.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to an apparatus for measuring near-acoustic vibrations, and more particularly to the measuring of seismic vibrations in severe environments, such as down-well holes or permanent sea floor installations.BACKGROUND OF THE INVENTION[0002]There is often a need to measure near-acoustic vibrations, such as seismic vibrations, in harsh environments. Traditional seismometers involve the suspension of a reference or proof mass within a frame and a sensor to measure the relative motion between the frame and the proof mass as seismic waves act on the frame to move it. In this manner, traditional seismometers require the use of a proof mass. Use of a proof mass limits the robustness of the seismometer, making seismometers not well suited to harsh environments.[0003]Optical sensors are well suited to such rugged environments because they have passive detective elements that are immune from magnetic noise and electrolytic corrosi...

AI Technical Summary

Benefits of technology

[0004]Embodiments of the present simple fiber optic seismometer utilize an optical glass fiber that reacts with suitable sensitivity and accuracy in response to accelerations. In this manner, it provides desired high levels of precision seismic sensing while being manufacturable at low costs. Thus, the simple fiber optic seismometer is well suited for harsh environments.

Problems solved by technology

Use of a proof mass limits the robustness of the seismometer, making seismometers not well suited to harsh environments.

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